import java.util.Deque;
import java.util.LinkedList;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: ws
 * Date: 2023-01-07
 * Time: 21:54
 */


public class BinaryTree {

    static class TreeNode {
        public char val;
        public TreeNode left;//左孩子的引用
        public TreeNode right;//右孩子的引用

        public TreeNode(char val) {
            this.val = val;
        }
    }


    /**
     * 创建一棵二叉树 返回这棵树的根节点
     *
     * @return
     */
    public TreeNode createTree() {
        final TreeNode treeNode = new TreeNode('a');
        final TreeNode treeNode1 = new TreeNode('b');
        final TreeNode treeNode2 = new TreeNode('c');
        final TreeNode treeNode3 = new TreeNode('d');
        final TreeNode treeNode4 = new TreeNode('e');
        treeNode.left = treeNode1;
        treeNode.right = treeNode2;
        treeNode1.left = treeNode3;
        treeNode1.right = treeNode4;
        return treeNode;
    }

    // 前序遍历
    public void preOrder(TreeNode root) {
        if (root == null) {
            return;
        }
        System.out.println(root.val);
        preOrder(root.left);
        preOrder(root.right);
    }

    // 中序遍历
    void inOrder(TreeNode root) {
        if (root == null) {
            return;
        }
        inOrder(root.left);
        System.out.println(root.val);
        inOrder(root.right);
    }

    // 后序遍历
    void postOrder(TreeNode root) {
        if (root == null) {
            return;
        }
        postOrder(root.left);
        postOrder(root.right);
        System.out.println(root.val);
    }

    public static int nodeSize;

    /**
     * 获取树中节点的个数：遍历思路
     */
    void size(TreeNode root) {
        if (root == null) {
            return;
        }
        nodeSize++;
        size(root.left);
        size(root.right);
    }

    /**
     * 获取节点的个数：子问题的思路
     *
     * @param root
     * @return
     */
    int size2(TreeNode root) {
        if (root == null) {
            return 0;
        }
        return size2(root.left) + size2(root.right) + 1;
    }


    /*
     获取叶子节点的个数：遍历思路
     */
    public static int leafSize = 0;

    void getLeafNodeCount1(TreeNode root) {
        if (root == null) {
            return;
        }
        if (root.left == null && root.right == null) {
            leafSize++;
        }
        getLeafNodeCount1(root.left);
        getLeafNodeCount1(root.right);
    }

    /*
     获取叶子节点的个数：子问题
     */
    int getLeafNodeCount2(TreeNode root) {
        if (root == null) {
            return 0;
        }
        if (root.left == null && root.right == null) {
            return 1;
        }
        return getLeafNodeCount2(root.left) + getLeafNodeCount2(root.right);
    }

    /*
    获取第K层节点的个数
     */
    int getKLevelNodeCount(TreeNode root, int k) {
        if (root == null) {
            return 0;
        }
        if (k == 1) {
            return 1;
        }
        return getKLevelNodeCount(root.left, k - 1) + getKLevelNodeCount(root.right, k - 1);
    }

    /*
     获取二叉树的高度
     时间复杂度：O(N)
     */
    int getHeight(TreeNode root) {
        if (root == null) {
            return 0;
        }
        int left = getHeight(root.left);
        int right = getHeight(root.right);
        return left > right ? left + 1 : right + 1;
    }


    // 检测值为value的元素是否存在
    TreeNode find(TreeNode root, char val) {
        if (root == null) {
            return null;
        }
        if (root.val == val) {
            return root;
        }
        TreeNode ret = find(root.left, val);
        if (ret != null) {
            return ret;
        }
        ret = find(root.right, val);
        if (ret != null) {
            return ret;
        }
        return null;
    }

    //层序遍历
    void levelOrder(TreeNode root) {
        if (root == null) {
            return;
        }
        Deque<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        while (!queue.isEmpty()) {
            TreeNode cur = queue.poll();
            System.out.println(cur.val);
            if (cur.left != null) {
                queue.offer(cur.left);
            }
            if (cur.right != null) {
                queue.offer(cur.right);
            }
        }
    }


    // 判断一棵树是不是完全二叉树
    boolean isCompleteTree(TreeNode root) {
        if (root == null) {
            return false;
        }
        Deque<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        while (!queue.isEmpty()) {
            TreeNode cur = queue.poll();
            if (cur != null) {
                //完全二叉树的层序遍历时叶子节点在末尾之前不能为null
                queue.offer(cur.left);
                queue.offer(cur.right);
            } else {
                //1. 检测到null结点
                //2. 直接退出
                break;
            }
        }
        //再次遍历queue
        //若没有到达最后的叶子节点，则null之后定会有一个不为null的右兄第的结点
        //若到达最后，则队列中全是null
        while (!queue.isEmpty()) {
            TreeNode cur = queue.poll();
            if (cur != null) {
                return false;
            }
        }
        return true;
    }
}